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WOLF BLITZER, CNN HOST: Boston police now say three additional people have been detained in the marathon bombing investigation. Let's bring back Ashleigh Banfield right now.

Ashleigh, you've been working this story.

What exactly do we know about these three individuals? I believe they're students at the University of Massachusetts, the Dartmouth campus there; what do we know about what's going on?

ASHLEIGH BANFIELD, CNN HOST: Well, this is in such the early offings (sic) of this story at this point. But our sources are telling CNN at this point, Wolf, that at least our Homeland Security sources are telling us that two of these students had contact with Dzhokhar Tsarnaev, may have been actually roommates with Dzhokhar Tsarnaev.

And at this point they're saying, these officials of firsthand knowledge are saying that they are New Bedford students, that they'd been arrested on charges of making false statements and also conspiracy to obstruct justice directly in connection with the case of the Boston Marathon bombings.

These were Dzhokhar Tsarnaev's roommates, apparently. The third suspect -- or the third person who's been arrested in this case and possibly facing the charges at the federal courthouse later today is also a student, but we are being -- we are being told that it is not Katherine Russell.

It's not Katy (ph) Russell, who was the -- who is the widow of Tamerlan Tsarnaev, the older brother who died in the shootout with the police the night before his brother was taken into custody.

Dzhokhar Tsarnaev's roommates had apparently, Wolf, been detained for quite some time now, several days on immigration violation charges, which surprised some of us, just in the fact that investigators had plenty of time to hold these two students if they wanted to have access to them or question them without having to actually officially charge them and start a timeline, a legal timeline rolling, in which you have to actually have your ducks in a row.

So it's interesting to hear that they have now actually been brought in on this suspicion. But again, this was a Homeland -- Department of Homeland Security source with firsthand knowledge of this, saying that these are two New Bedford students arrested on charges of making false statements and conspiracy to obstruct justice in the case of the Boston Marathon bombings.

The third student arrested is a U.S. citizen, we're also told. The Boston police, Wolf, and I'm just getting details as I'm talking to you, so you'll have to just bear with me.

The Boston police said the three additional people have been taken into custody. They date the marathon bombings, which we all know now, as April 15th. And I have additional information just, again, with the Homeland Security official, who has spoken to CNN, but I do want to add this as well.

And perhaps, Wolf, this is the most significant reporting for the people who live here in Boston where I am, many of them daily coming out to see the messages and the tributes that have been left behind for those who were killed and injured in those bombings.

The police in Boston wanted to make sure people know there is -- and I'm going to quote them -- "There is no threat to the public," Wolf, after announcing that these three people had been taken into custody, "no threat to the public."

Significant for those who live here, perhaps maybe even significant for the Miranda timing as well, which we all know there is a public safety exception which precludes you from having to Mirandize as quickly as perhaps other suspects in the case.

I do also want to also reiterate, Wolf, very importantly that at this time is no tie to the actual bomb making or the carrying out of the actual crime itself with regard to these suspects. These are all issues after the fact, as we're being told by the Homeland Security source. So just a lot that's developing at this point, live on location right here in Boston, Wolf.

BLITZER: Ashleigh, stand by for a moment. Let's get some legal analysis of what's going on.

Professor Alan Dershowitz is there on the ground in Boston. He's the Harvard Law School professor He's joining us right now.

Alan, let's go through these specific charges. If these students, at least two of them have been arrested on making false statements and conspiracy to obstruct justice, we know they've been questioned now over the more than two weeks, basically going back to the days of -- that they discovered -- nearly two weeks, I should say, the day they discovered the Tsarnaev brothers were involved in this.

And these were the roommates, if you will, students, colleagues of the younger Tsarnaev brother, what do you make of these two specific charges, making false statements, conspiracy to obstruct justice?

PROF. ALAN DERSHOWITZ, HARVARD LAW SCHOOL: Well, they are typical charges that grow out of these kinds of investigations. Many people don't realize that if you lie to any federal official, even if it's a little white lie or an innocent lie or an exculpatory lie, saying, well, I didn't know anything; I really didn't know anything, any lie of that kind can be a federal crime. Also, if you help somebody destroy evidence or hide evidence or conceal information, that can be an obstruction of justice.

And if you do it together with that person, it's a conspiracy to obstruct justice.

So what we know is, number one, they haven't been charged with anything relating to the making of the bomb or the planting of the bomb. Everything they've been charged with relates to what they did after the bombing occurred.

And they're serious crimes. Probably they're being charged in order to squeeze them, in order to get them to provide more information on the threat they will not only be deported but also prosecuted for these serious crimes that carry years in prison.

BLITZER: Two of them apparently from Kazakhstan, one a U.S. citizen, what different if any does it make about in this particular situation if they are legal residents, student visas or whatever here in the United States or if they're U.S. citizens?

DERSHOWITZ: Well, it just gives more power to the federal government to pressure them if they are not citizens. They can be both prosecuted and deported if they're not citizens.

If they are citizens, they can still be prosecuted. The criminal law doesn't apply differently to citizens and to noncitizens, but the immigration status, the ability to detain them, as two of them were detained previously, based on their not being citizens and being out of, kind of, sync with their papers gives the government far more authority in detention and also more flexibility in how to deal with them.

But other than that, in terms of criminal charges, it's identical.

BLITZER: All right. Alan Dershowitz, hold on.

Ashleigh Banfield, hold on.

Tom Fuentes, the former FBI assistant director, now the CNN law enforcement analyst, is joining us right now.

What do you make of this, the breaking news right now? Three additional people, we believe students from the University of Massachusetts Dartmouth campus, have now been arrested, Tom?

TOM FUENTES, CNN CONTRIBUTOR: Wolf, I think it says that the FBI was suspicious of them from the very beginning and used the fact that they were illegally here, overstaying their student visa, as the reason that would allow them to detain them long enough to develop the evidence that they needed to bring the charges today.

So this is -- these are a couple of people that they were already wondering from the beginning if they could have been helping the brothers either before, during or after the bombing.

(CROSSTALK)

FUENTES: My information is --

BLITZER: Go ahead, Tom. What's your information?

FUENTES: Just that these charges have to do with after the bombing, that helping dispose of evidence, which is obstruction, everything Professor Dershowitz just mentioned, that lying to the FBI, obstruction of justice and (inaudible) because there were a couple of them doing it together, that makes it conspiracy.

BLITZER: Tom, hold on for a moment, because Drew Griffin is joining us on the phone. He's been speaking to an attorney for, we believe, one of these three.

Is that right, Drew? One of these three who's been arrested?

Unfortunately, I think we've lost our connection with Drew. We'll get back to Drew in a moment. Tom Fuentes is still with us.

Pick up that final thought you were making, Tom, on the information you're getting.

There's no evidence to believe, no suggestion that any of these three may have been directly involved or even indirectly involved in the actual planting of a bomb or building of a bomb, anything before the Boston Marathon bombing, but they may -- the keyword may -- allegedly have been involved in helping to cover up evidence or mislead police, is that right?

FUENTES: Right. That's correct, Wolf. It doesn't mean that they weren't involved in helping in the bombing, it just means that as of now they're not going to be charged with helping them. The police says that they were not, but they are still working the investigation.

But they are going to go ahead and bring the charges now that, after the fact, they may have disposed of items that could have been considered evidence and, in addition, made false statements to the FBI.

And again, under the law, you do not have to talk to the FBI in an official investigation, but if you do, you have to tell the truth. And so apparently they did talk, but were not truthful and at least they can demonstrate a lack of truthfulness at some point, which is why they're charging them.

BLITZER: They're being charged with making false statements and conspiracy to obstruct justice.

Drew Griffin, I think we've connected with you. Drew, you've spoken with an attorney for one of these three, is that right?

DREW GRIFFIN, CNN CORRESPONDENT: Yes, Robert Stahl (ph) is the attorney for Dias Kadyrbayev and (inaudible) Kadyrbayev (ph) and confirms to us that the photo that we've been looking at for a couple of weeks now in the Times Square, that his client is in the center of that picture, Wolf.

And according to Robert Stahl (ph), the second suspect now we know is next to him, basically standing on the right side of his client.

So the three people at the center of the picture are the one who is are involved with this. And I might add that the attorney that we have been speaking to for quite a while was pretty adamant early on that his client had nothing to do with the bombing or the plot.

But as Tom Fuentes just said, may have been wrapped up in some lies when the FBI came calling. This was the Friday after the bombing.

BLITZER: Because -- so you're speaking to Robert Stahl (ph), I just want to be precise, who is the attorney representing one of these Kazak students. His name is Dias Kadyrbayev. And there was another Kazak student you were pointing out as well. His name is Azamat Tazhayako. So there's two.

What about the third person arrested? Do we know anything about the third person, apparently a U.S. Citizen?

GRIFFIN: Have no knowledge whatsoever about that. There was a third student, as you recall, briefly detained but released last Friday, who was in the same apartment with these two Kazakh students. We believe that person was a female and that she was a U.S. citizen. But we have no idea if that person is the third person involved.

I know that we have many other reporters who are going through official channels to find out who the third person charged is here, Wolf. But at this time we just really don't know.

BLITZER: And we do know because of good reporting by David Fitzpatrick of CNN Special Investigations unit this goes back about 10 days or so ago that these two Kazakh students, Drew, they were picked up and questioned for about 10 hours by the FBI back on April 19th, just hours after the younger Tsarnaev brother surrendered to authorities. He was hiding out in that boat in Watertown, Massachusetts.

During these past 10 days, have these Kazak students been detained, have they been held or have they been free?

GRIFFIN: Yes. What happened was is they were initially detained. And then I believe we even have pictures of them taken into custody with handcuffs on that Friday. It was a raid that took place prior to Dzhokhar Tsarnaev's capture.

And we were told specifically that the reason there was such a heavy handed raid on that apartment is because they thought Dzhokhar Tsarnaev might be in that apartment.

These two students and that third student I mentioned were all released. And then the next day Immigration and Customs control officers came back and placed these two Kazak students in custody based on student visa violations.

They have remained in custody or detention since that time, which, Wolf, is somewhat unusual for a student visa violation.

But our sources were telling us at the time this was out of the abundance of caution. They wanted to make sure they had these two students as the investigation was progressing into what actually (inaudible) Boston Marathon and now some two weeks later these two students have apparently been charged.

BLITZER: Yes, formally charged. And we're going to get more specifics in the next few hours.

And as we reported a while ago after they were detained, these two Kazak students, we reported immigration law requires that students who are here on legitimate student visas, quote, "regularly attend classes if they want to maintain those student visas."

But they said that Kadyrbayev, at least one of the students, did not -- had not been attending classes. And that was the reason they gave for keeping him under detention.

Drew, stand by.

Everyone stand by. We're following the breaking news out of Boston. There have been three arrests in connection with what's been going on in the Boston investigation, the bombing investigation. And we're going to continue the breaking news coverage right after this.

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BLITZER: There is breaking news coming out of Boston. We're following it right now.

Three arrests, three additional arrests, three students arrested, students, we believe, from the University of Massachusetts' Dartmouth campus, friends, associates of the younger Tsarnaev brother, Dzhokhar Tsarnaev, who's now being held in a prison outside of Boston himself.

Susan Candiotti is getting new information for us. What else are you picking up, Susan?

SUSAN CANDIOTTI, CNN NATIONAL CORRESPONDENT: Hi, Wolf. This new information now gives us a clearer picture of what these charges are about.

Remember that we are hearing from two U.S. government sources that they involve lying to investigators and a conspiracy to obstruct justice.

As to the lying, according to U.S. federal law enforcement official, I am told it involved knowing about the whereabouts or lying about seeing one or both of the suspects after the bombing.

So the students allegedly did not tell the truth about seeing them or knowing about their whereabouts after the bombing took place.

The second charge involving obstruction of justice involves them being involved, allegedly, in throwing out items from that dorm room that they shared with Dzhokhar, throwing things into the dumpster and getting rid of them.

Now, let's remind you what we've been reporting about that. We have been reporting that what led authorities to the landfill for that two- day search last week came in part from information, leads they were getting from the suspect himself, but also other investigative leads.

Those leads are also came from, I am told from our source, from the interview with these students.

So that is important new information, Wolf, that we're learning to help clarify what this is about.

And we want to remind you as well that the Boston police department is saying that the arrest of these three individuals does not pose any public threat or threat to public safety at this time.

We also do expect that as early as this afternoon that these three individuals will be making their first appearance in court to these charges as early as this afternoon, Wolf.

BLITZER: The court -- and which court are we talking about? In New Bedford, is that right?

CANDIOTTI: We're talking about the landfill -- that's right, in New Bedford near the University of Massachusetts' Dartmouth campus.

BLITZER: I mean, they would appear in a local court? This is not a federal charge.

Is this -- this would be a local courtroom in New Bedford, Massachusetts, right?

CANDIOTTI: No, Wolf. These will be federal charges.

BLITZER: These are federal charges.

CANDIOTTI: These three individuals are now in the custody of the FBI. That is correct.

BLITZER: OK. I want to be precise. They're not in custody of local police. They're in custody of the FBI, so this is obviously a much, much bigger deal if the FBI has decided to bring these formal charges ...

CANDIOTTI: Oh, absolutely.

BLITZER: ... against them before a federal judge.

CANDIOTTI: Yeah, and the way that this came down is that the Boston police department put out a tweet that three people were in custody, so naturally the initial thought was they're in the custody of the Boston police department.

But the Boston police said, no, they're in the custody of the FBI and we're being referred to federal authorities for more information on the charges. Now those charges as we understand it have not yet been publicly revealed at this time. This is what we're learning about them from our sources.

BLITZER: Has the FBI put out any statement yet?

CANDIOTTI: Not as yet. Not as yet. They are, you know, telling us to hold tight. Same thing from the U.S. attorney's office. We'll have to wait and see.

And that's why we continue to work our sources, our sources that we have been talking with continuously throughout and giving us very good information about this investigation, Wolf.

BLITZER: But we have confirmed the FBI is now custody of these three students.

Brian Todd is also working the story. What else are you picking up, Brian?

BRIAN TODD, CNN CORRESPONDENT (via telephone): Wolf, we have confirmation from the attorneys for both the Kazakhstani students who were detained on immigration charges, confirmation from these attorneys that those two students are -- have been arrested in connection with this.

The attorney, Harlan Protass -- he represents student Azamat Tazhayakov -- confirms his client and the other student named Dias Kadyrbayev are two of the three students under arrest, in custody now.

And one source close to -- familiar with the investigation tells us they're understanding is they'll be charged with some form of obstruction of justice, whether it's conspiracy or maybe conspiracy to obstruct.

That is what they know now. And they are expected where I am at the John Joseph Moakley Federal Courthouse in Boston at some point this afternoon. They're expected to make an appearance here at some point this afternoon.

Neither of these two sources could give us the name of the third suspect.

BLITZER: The third suspect being a U.S. citizen as opposed to the Kazakh students, and they will appear, we suspect, later this afternoon before a federal judge in Boston.

Anything else you're picking up, Brian?

TODD (via telephone): Just that there is a swarm of media out here outside the courthouse now, Wolf, waiting for any word.

We're watching entrances, front and side, to see if any sign of these suspects arriving. And, of course, we're trying to dig on a name of the third suspect. We don't have it just yet.

BLITZER: And I just want to show that picture once again, those two Kazakh students who have now been arrested by the FBI.

This is when they visited last year. They visited Times Square together with Dzhokhar Tsarnaev, the 19-year-old suspect in the Boston marathon bombing.

Two other students, two other friends, we're not showing their pictures, but we are now showing the two Kazak students together with Dzhokhar Tsarnaev.

Lawrence Crook, one of our CNN assignment editors, is joining us right now. Lawrence, you witnessed when these guys were picked up, these two students, is that right?

LAWRENCE CROOK, CNN ASSIGNMENT EDITOR: Yes. I was in New Bedford when the two, Azamat and Dias, students were taken into custody.

We had learned through Jason Kessler (ph) on our desk on Friday night that three people had been taken into custody off Carriage Drive in New Bedford. This is a very residential neighborhood. There's a lot of students that live in this neighborhood.

So on Saturday, me, myself and Jay McMichael (ph), one of our photo journalists, went down there to check out the scene. We were there with several media and we went to the door.

I had knocked on the door and asked if I could speak with Azamat and Dias, and they both kind of laughed at me, looked at me, very pretentious almost. They were having a great time with the media being out front. They were taking video and photos of us.

At one point it looked like they were going to try to talk to us, but one of the photographers on scene started snapping photos and scared them back into the room.

We were there for about five to six hours. And, eventually, the DHS, Homeland Security and a (inaudible) van pulled up, were inside the house for about an hour and then we have video of them being taken out in handcuffs, Azamat and Dias, and brought off to an unknown location.

There is a third person that lives in that building with Azamat and Dias. We were told by neighbors that it is either the ex- or the current girlfriend of the younger suspect, Dzhokhar Tsarnaev.

We're not sure whether or not she's the person that's in custody, the third person, but she was living in the building with Azamat and Dias. I tried to speak to her as well. She didn't want anything to do with me.

We did not see her taken out into custody. This is just presumption, but she was in the building and had been taken into custody Friday night. All three of them had been released and then authorities came back the next day and took Azamat and Dias into custody.

BLITZER: And I just want to show our -- remind our viewers these are the two Kazakh students visiting Times Square last year with Dzhokhar Tsarnaev. The Kazakh student, Dias Kadyrbayev and the other student, Azamat Tazhayakov. These are the two Kazak students who were arrested today by the FBI.

There's a third person, a U.S. citizen, arrested as well. We have not yet identified that third person. We're getting more information.

We'll resume the breaking news out of Boston right after this.

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BLITZER: We're continuing breaking news coverage out of Boston. Take a look at this picture taken last year at Times Square. You see to the right you see Dzhokhar Tsarnaev. He's under arrest as we all know one of the suspected Boston bombers.

But take a look to the left. Two individuals, two students from Kazakhstan at the university of Massachusetts at Dartmouth. On the left -- second from the left -- we're covering up the first person, but the second from the left that's Azamat Tazhayakov.

And right in the center of the picture, Kadyrbayev, the other student arrested, we believe on charges of making false statements to authorities and conspiracy to obstruct justice, serious charges right now.

Let's bring in Juliette Kayyem. She's been watching what's going on. She's a former official of the Department of Homeland Security, a columnist for "The Boston Globe."

What do you make of these dramatic developments, three arrests, two individuals we've identified, we don't know the third person, Juliette, but we do know the third person is a U.S. citizen?

JULIETTE KAYYEM, CNN NATIONAL SECURITY ANALYST: So the pieces look something like this. Almost immediately after the bombings and during that investigation, everyone remembers, there was this interviewing, late-night interviewing and custody of three people in an area called New Bedford. That's a southern coastal town from here. That then goes away a little bit.

This morning, two of those individuals were before an immigration judge, very different than federal criminal charges. This is one of those sort of jurisdictions -- they were on student visas -- part of the post-9/11 architecture includes much more stringent guidelines on student immigrants. They have to prove they're still in a university, in college.

This morning, two of them appeared before the immigration judge and appear not to have known that they were about to turn around and face these criminal charges. So that's what we have right now.

So there were two parallel paths going on, the immigration charges, which are not criminal, but if you're an immigrant and violate your immigration status, we can still put you before a judge. And then now the much more serious criminal charges.

But just to be clear to everyone, the Boston police tweeted this first. I think that was -- I know that that was because, you know, we're still a little bit anxious here. They wanted to get ahead of what is obviously a concern that there might be more attacks, making it clear that there's no public safety harms or any public safety threat at this time.